If you've done a masters level thesis and then moved to doctoral work,

[Macrina]

How closely did your masters level thesis match your doctoral proposal? And how long was the thesis?

I'm currently in an advanced masters program, starting to think about my thesis. The topic I'll be writing on is pretty close to what I would propose for a doctoral program.

Bad idea? Or good idea? The topic is big enough for several books' worth of research/writing, and I hope that my thesis will help me to fine-tune and focus before I do doctoral apps. On the other hand, I would hate to look like my focus is too narrow and perhaps overdone.

If you've moved on to doctoral work after a significant thesis, how closely related were they? Any advice to someone thinking about two research projects on related/similar topics?

[Kuriakos]

So far, my 100-page ThM thesis will have nothing to do with my dissertation, but it would not be a problem if they were related. It is expected that you will try to expand on research you've already completed. That is part of moving from a masters student to a doctoral student. As long as you realize that you are not actually writing the first one or two chapters of your dissertation and you are open to the fact that doctoral coursework will push you in new directions, then I don't see how this could be an issue.